1. Field of the Invention
The present invention relates to a stack module, and more specifically to a stack module in which a plurality of substrates onto which are installed a semiconductor chip are stacked.
2. Description of Related Art
FIG. 3 shows a cross sectional view of an example of a stack module in the related art.
In the stack module which is shown FIG. 3, a heatsink 8 is adhered to the top of (or the beneath of) a semiconductor chip 1 (or substrate 2), that rests on (or beneath) the substrate 2, and four of these combinations being stacked using a bump 6 for the purpose of connecting the substrate.
On the other hand, for example, in the Japanese Unexamined Patent Publication (KOKAI) No. 5-190712, discloses a semiconductor device in which a heatsink is directly connected to one main surface of a semiconductor chip but this reference fails to show or suggest to stack a plurality of this kind of semiconductor chips.
However, there is a drawback in the above-described stack module, because of the difference in coefficient of thermal expansion between the semiconductor chip (or substrate) and the heatsink, which causes thermal stress to develop at the above-noted adhered part, thereby shortening the thermal-cycle life.
Additionally, because the heatsink is a flat plate and has a small heat-radiating surface area, to increase the cooling effect, it is necessary to extend the heatsink to outside the bounds of the substrate, this making it difficult to achieve a compact stack module.
In view of the above-noted drawbacks in this related art, an object of the present invention is to provide a stack module which enables efficient cooling without the generation of thermal stress therewithin, thereby enabling long life of the stacked module.